Lubricant



Patented Dec. 29, 1936 LUBRICANT William Stansiield Calcott, Woodstown, and Robert Calvert McHarncas, Carney; Point, N. J., assixnors to E. L du Pont de Nemours &

Company, Delaware Wilmington, DcL, a corporation of No Drawing. Application April 24, 1934, Serial No. 722,130

30 Claim.

This invention relates to lubrication and par ticularly to the improvement of extreme pressure lubricating characteristics of lubricants by the addition of assisting agents.

The advantages of a high pressure lubricant become apparent when the present trend in design of automotive and other machine parts, and the increased strength of metal parts, due to the use of alloy steels, is considered. The presm sures ordinarily found in well lubricated journal bearings do not exceed 2,000 lbs/sq. in. and for conditions such-as this a film of heavy oil can be expected to remain between the rubbing surfaces. When gears are considered. where the 15 contact between surfaces is of very small width, the bearing pressures often reach values as high as 25,000 lbs/sq. in. Under such extreme pressure, it is unlikely that any oil or grease can be obtained which willbe viscous enough to pre- 20 vent metallic contact. The result of the lack of a lubricating film between the rubbing surfaces results in scoring and scuffing of the gears.

Failure to maintain lubricant films on idle bearing surfaces is now well recognized as the cause of 70 to 80% of the wear occurring on cylinder walls of automotive and other internal combustion engines. When an engine is stopped, the oil film on the vertical surfaces soon drains ofl and, when the machine is again started up, an appreciable time elapses before the circulation provides oil for the formation of new' lubricant films. An assistant which, when added to the motor oil, will prevent the separation of the 011 film from the metal should prevent a large part of the wear now occurring.

Prior to this invention various assistants have been added to oils to improve their lubricating properties. Among such assisting materials which have been used are sulfur, sulfur chloride, 40 sulfurized oil or oil containing naturally occurring sulfur, various heavy metal soaps and aluminum soaps, castor oil and, recently, allphatic and aromatic halides. While some -of these assistants, such as the sulfur and the organic halides improve the lubricating properties of the oil to a great extent, they have not proved to be satisfactory for use for the reason that they are corrosive or give rise to corrosive agents by hydrolysis or oxidation. Also, this corrosive action is greatly intensified by the presence of small amounts of water. Some of the alkyl halides are volatile and, hence, are soon lost.

Other assistants such as the alkali and heavy metal soaps have proved to be of little value in improving the lubricating properties of the oils.

An object of this invention is to provide materials which, when brought into contact with metal bearing surfaces will form a lubricating film between such bearingsurfaces which lubri eating film will adhere to the metal surfaces and resist high pressures. A further object of this invention is to provide materials which, when added to lubricating media, improve their properties, particularly their adhesiveness and resistance to high pressure. A further object is to provide a method for retarding wearing and seizing of bearing surfaces. Other objects are to provide new compositions of matter and to advance the art. Still other objects will appear hereinafter.

These objects may be accomplished in accordance with our invention which comprises contacting metallic bearing surfaces with combinations containing a nitro aromatic group and an amino group. Such combination may comprise two separate compounds one of which is a nitro aromatic compound and the other an amino compound. Also, the combination may consist of a single compound containing both a nitro and an amino group in the same molecule.

When such a combination is brought into contact with a metal bearing surface, it forms a noncorrosive lubricating film which will retard the wear of the bearing surfaces, will withstand high bearing pressures and will preventmetallic contact of the bearing surfaces under high hearing pressures. The films have low friction coefiicients and exhibit exceptional lubricating properties at all pressures and rubbing speeds but are particularly valuable at high pressures. Such films will not be washed from the bearing surfaces by water, oil or ordinary organic solvents such as gasoline, naphtha and the like.

The combination containing a nitro aromatic group and an amino group may be employed by itself as a lubricant. However, it will generally be found to be preferable, for economical reasons, to employ it in a liquid carrying medium or a grease. The liquid carrying medium may be any liquid in which the combination may be dissolved, dispersed or emulsified. It will also be generally preferred to employ the combination in an oil or grease as the combination is particularly effective in such media.

Among the combinations which wehave found to be particularly effective are:

Our combinations may be employed in an oil or other medium in extremely small amounts;

However, it will generally be found desirable to use them in amounts of at least 0.1% of the oil. Further, the amounts added to the oil or other carrier will be largely dependent upon the matwo parts a-nitro naphthalene chinery in which it is, applied and the area oi! the metal surfaces with which it will be brought into contact.

The method of testing our compounds was that devised by J. O. Almen (Oil and Gas Journal, 30, 109, 1931). This method consists of running a diameter drill rod between two halves of a split bushing which is maintained stationary. The load on the bushing is controllable and provision is made for measuring the torque developed by the friction of the lubricant film. A hydraulic system for increasing the loading on the bushing until the oil film breaks and the metal seizes is provided. The rubbing speed is about 50 feet per minute and the method of loading is gradual, one weight being added to the loading lever each ten seconds. Each weight added to the loading lever increases the pressure on the bushing by about 125 lbs. The machine provides torbeam loadings up to 20 weightJswhich corresponds to a pressure of 20,000 lbs/sq. in. on the full projected area of the drill rod. The bearing surface of the bushing is cut to a diameter 0.007 inch larger than the drill rod so that, before any wear occurs, the actual bearing surface is a line. As wear occurs, the bearing surface widens but seldom covers the bushing. After a test, the width of the bearing scar can be measured and an approximate value for the actual bearing pressure obtained. The values given in the following examples' represent the calculated actual bearing pressures which were reached in the tests without failure of the film. These values represent film strength or film resistance.

when subjected to the above test, a good grade of paraffin oil will withstand a pressure of only 3 to 5,000 lbs/sq. in. When an oil containing sulfur is tested by the same method, such oil will show a film strength of about 20,000 lb./sq. in. and will give a torque reading of about 4.7 lb. it. at this load.

In order to more clearly illustrate our invention and the advantageous results to be obtained thereby the following examples are given:

Example I One hundred parts of an SAE 30 oil to which one half part of a-nitronaphthalene and one half part alpha-naphthyiamine has been added carried a load on the Almen machine of 26,000 lb./sq. in. with a friction torque, at this load, of 2.9 lb. ft.

Example I1 One hundred parts 01 an SAE 30 oil was compounded with one part m-dinitro benzene and 1 part alpha-naphthylamine. This mixture withstood 'a load of 28,000 lb. per sq. in. where the torque was 3.2 10. it.

Example III A compounded lubricant containing about two parts dibutylamine, about one part m-dlnitro benzene and ab'out'98 parts of a naphthenic lubricating oil withstood a pressure of 12,000 lb./sq. in. and dtveloped a torque of 2.2 lb. ft.

ltxample IV One hundred pa pounded with about 2 of lubricating oil was comparts or aniline and about and withstood a test pressure of 25,000 lb./sq. in. The friction torque developed was 2.8 lb. ft.

Example V A composition comprising one part amino azo benzene, about two parts a-nitronaphthalene and parts lubricating oil withstood a load of 28,000 lb. per sq. in. The torque was 3.4 lb. It.

Example VI One part of parts of lubricating 011 showed a film strength 'of 21,000 lb. per sq. in. The torque was 1.8 lb. it.

Example VII Example vm A mixture of 50 parts by weight ore-mm naphthalene and 50 parts amaphthylamine,

tested alone on the Almen machine, film strength of 36,000 this load of 1.8 lb. ft.

Example IX One part of a mixture 'of equal parts of a-nitro naphthalene and a-naphthylamlne was mixed with 50 parts of lorol alcohol. This mixture withstood a test pressure of 10,000 lbs/sq. in. The torque was 1.0 lb./ft.

Example X mixture containing equal parts of a-nitro naphthalene and a-naphthylamine was compounded with 20 parts of benzene. The test load held was 16,000 lbs/sq. in.

Other combinations which have proved to be efifective and the results obtained by the use showed a lb./sq. in. and a torque at One part of thereof in a medium (SAE 30) naphthenic oil aregiven in the following table:

Table Almen test results Amino compound Nitro compound as m b-Naphthylamlnc 1 a-Nitronaphthalene. 2 21,000 2. 1 Aniline 2 Nih'obenzene 2 17,000 1.0 Anilino 2 2:4-Dinitrophenol..- 1 12,000 1.5 m-Toluylene diamino 1 Nitrobonzene 5 17,000 1.8 1 2:4-DiniLrophenoL. l 18. 000 1. 0 1 a-Nitronapbtbalene. 2 17,000 1.6 Do 1 m-Dinitrobonzene..- 1 20,000 2 0 Dicyclohex y l amine 2 2:+Din1tr0phenol. 1 15.000 1. 4 Do 2 n-Nitronaphthalene. 2 .16,000 1. 8 Aminoawbenzeno. l ZM-D'mltmphepol..- 1 15,000 1.7 Do l m-Dinltrobenzeno. 1 15,000 1.8 Dibutylamine 2 Nitrobenzene 2 12,000 '2 9 b-Amino anthraquinone .3 a-Nitronaphtbalene. 2 12,000 3.1 Anthranilic acid." 5 a-Nitronaphthalene. 2 13,000 1. 7 Do 5 Nitrobenzene 2 15,000 1. 8 Lauryl nmiue i Nitrobenzene 2 14.000 1.4 Tetrahydrocarba- 1,010 l m-Dinitrobenzene .5 17,000 2.2

- As a general, rule, any nitro aromatic combe employed with any amine. Howusually be undesirable to employ compounds containing more than two nitro groups in a single nucleus, because of the explosive properties of such compounds. Also the nitro aromatic compounds in which the and nucleus belongs to the benzene, biphensl and naphthalene'series will generally be preferred 2-nitro a-naphthylamine and 99 because of their lower melting points, greater solubility and reactivity.

The primary amines will usually be preferred. However secondary and tertiary amino compounds of the aliphatic, aromatic and cyclic series may also be employed. Some of the other types of amino compounds which may be mentioned are the amino phenols, represented by p-amino-phenol, hydroxyl amines, hydrazines as phenyl hydrazines, amino biphenyls, nitrosoamines, amino thiazoles as l-amino benzothiazole, morpholines, pyridines, piperidines, pyrroles, pyrrolidines, acridines, amino acids as amino acetic acid, ureas, thioureas, guanidines and aldehyde amines as hexamethylene tetramine and the like.

We believe that, when the nitro aromatic compounds'and amino groups are present in separate compounds employed in combination, the compounds react with each other in the oil or other medium adjacent the bearing surfaces to form complex compounds. We believe that such complex compounds are the active materials in the formation of the films on the metallic bearing surfaces. However, we do not wish to be restricted to any theory as to how our compounds produce their eifect. Accordingly, the nitro compound may be caused to react with the amino compound, under conditions similar to those prevailing at the bearing surfaces, prior to their incorporation into the oil or other medium and such reaction products come within the scope of our invention.

Other combinations containing nitro aromatic groups and amino groups, than those heretofore mentioned, may be employed and will be readily apparent to those skilled in the art. When the nitro group and the amino group are in separate molecules or compounds, the relative proportions of nitro aromatic compounds and amine may be widely varied. However, for the best results, it will generally be found desirable to employ from about 1 to about 5 parts of the nitro aromatic compound to about .3 to about 2 parts of the amine.

Our combinations may be employed in other liquid media such as vegetable oils, kerosene, naphtha, alcohols, benzene, gasoline, diphenyl, diphenyl oxide and any other liquid media in which our compounds may be dissolved, dispersed or emulsified.

The use of cutting oils in machining operations is well known. The cutting fluid has two functions; the first to provide a lubricant to reduce the friction between the cutting tool and the work, and the second to provide a means for cooling the work.

The general practice is to use either an oil or a dispersion of oil in water. The oils used vary considerably depending on the particular operation and may vary from a light mineral oil to a heavy mixture of mineral and animal oils. The water suspensions are usually made up from oils by the addition of dispersing agents of the Turkey red oil type. Recently the practice of adding sulphur or sulphur compounds has become common.

Die shaping of sheet metals and drawing of sheets and wires and tubes has also recently been improved by the use of a lubricant between the contacting surfaces.

Cutting oils are now generally made up by compounding about parts of lard 011, one to five parts of sulfur, two to ten parts of 'a petroleum sulfonate or Turkey red oil and about 60 parts of mineral oil. This mixture is then usedundiluted or dispersed in water which improves its cooling properties.

The lard oil, of course, breaks down under the high temperature conditions of use resulting in the formation of disagreeably odorous materials. The presence of sulfur, as in motor and gear lubricants, is a possible source of corrosive material necessitating the careful washing of machined parts before use. These oils have also iven considerable trouble from infection of the workmen which is only partially eliminated by the incorporation of a bactericide in the oil.

Wire drawing also requires an extreme pressure lubricant. Several types are in use but essentially they are the same as the ordinary cutting oils.

The pressures between the r bing surfaces during all machining operations are obviously very high as they result in deformation of the metal. This is, therefore, another problem of extreme pressure lubrication.

Our combinations of our invention may be employed in oil, oil emulsions or other suitable media as cutting oil compositions with the attending elimination of the odors and corrosiveness which are objectionable properties of most prior cutting oils. They willbe effective at very low' concentrations in such media. Other improvements similar to those observed on bearing lubrication should also result from such use. Decreased friction, safety from corrosion, and improved quality of the work are important results of their use.

The compounds of our invention are in general well known and the methods for making them are also well known and described in the literature. Accordingly, a detailed description of the methods employed for making the compounds referred to in this application is believed to be unnecessary.

From the preceding description it will be ap parent that the combination of a nitro aromatic compound and an amine are suitable assistants to be added to lubricating oils, greases and other liquids to form lubricating compositions for metallic surfaces and which will be effective at extreme pressures and under high rubbing speeds.

The combinations of. our invention, when brought into contact with metallic bearing surfaces, apparently form an adherent film thereon which film will withstand high bearing pressures without breaking down and thus will prevent metallic contact of the bearing surfaces. When incorporated in an oil or grease they cause the oil and grease to adhere more firmly to the bearing surfaces. This is a particularly desirable and advantageous characteristic of our compounds particularly adapting them for use where the bearing surfaces are vertical and an ordinary oil tends to drain therefrom, as in the cylinders of internal combustion engines. Furthermore, the film produced by our combination of compounds remains on the bearing surface even after the oil or other carrying media has been drained oil and continues to exert its effect until worn 05. Such film will not be removed by washing with water. gasoline, solvent naphtha or other ordinary organic solvents.

Under ordinary conditions of use, our combinations are noncorrosive and do, not, in general, induce corrosion of metal by water. They are effective where the rubbing speeds are high as well as where they are low, as in gears. When incorporated in lubricating oils and greases they form lubricants which have extremely low friction co eflicients.

While we have disclosed specific embodiments of our invention, it will be readily apparent to those skilled in the art that many modifications and variations may be made therein without departing from the spirit of our invention. Accordingly, the scope of our invention is to be limited solely by the appended claims construed as broadly as is permissible in view of the prior art.

We claim:

1. A lubricant assistant comprising a member of the group consisting of about 1 to about 5 parts of a nitro aromatic compound in combination with about 0.3 to about 2 parts of an amine of the group consisting of aromatic and aliphatic amines and reaction products thereof.

2. A lubricant assistant comprising a member of the group consisting of about 1 to about 5 parts of a nitro aromatic compound in combination with about 0.3 to about 2 parts of an aromatic amine and reaction products thereof.

3. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of a lubricant assistant of the group consisting of a nitro aromatic compound containing an amino group, the combination of about 1 to about 5 parts of 9. nitro aromatic compound and about 0.3 to about 2 parts of an amino compound and the products formed by the chemical reaction oi about .1 to about 5 parts of a nitro aromatic compound and about 0.3 to about 2 parts of an amino compound, and at the same time chemically acting upon such surfaces by means of said lubricant assistant.

4. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least'0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a nitro aromatic compound and about 0.3 to about 2 parts of an amino compound, and at the same time chemically acting upon such surfaces by means of saidlubricant assistant.

5. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of a lubricant assistant comprising the combination of about i to about 5 parts of a nitro aromatic compound and about 0.3 to about 2 parts of an aromatic amine and at the same time chemica y acting upon such surfaces by means of said lubricant assistant.

6. The method of retarding wearing and seizing 01 metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a nitro aromatic compound and about 0.3 to about 2 parts of a naphthylamine and at the same time chemically acting upon such surfaces by means of smdlubricant assistant.

'I. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of alubricant is assistant comprising the combination of about 1 to about 5 parts of 9. nitro naphthalene and about 0.3 to about 2 parts of an amine, and at the same time chemically acting upon such surfaces by means of said lubricant assistant.

8. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5' parts of a nitro naphthalene and about 0.3 to about 2 parts of a naphthylamine, and at the same time chemically acting upon such surfaces by means of said lubricant assist- 9. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant of the group consisting of 9. nitro aromatic compound containing an amino group, the combination of about 1 to about 5 parts of 9. nitro aromatic compound and about 0.3 to about 2 parts of an amino compound and the products formed by the chemical reaction of about 1 to about 5 parts of 9. nitro aromatic compound and about 0.3 to about 2 parts of an amino compound.

10. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a nitro aromatic compound and about 0.3 to about 2 parts of an amino compound.

11. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a nitro aromatic compound and about 0.3 to about 2 parts of an aromatic amine.

12. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of 9. nitro aromatic compound and about 0.3 to about 2 parts of a naphthylamine.

13. Lubricating oils and greases having incorporated therein at least-0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a nitro naphthalene and about 0.3 to about 2 parts of an amine.

14. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a nitro naphthalene and about 0.3 to about 2 parts of an aromatic amine.

15. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a nitro naphthalene and about 0.3 to about 2 parts of a naphthylamine.

16. A lubricant assistant comprising a member of the group consisting of a nitro aromatic compound containing an amino group, about 1 to about 5 parts of a nltroaromatic compound in combination with about 0.3 to about 2 parts of an amino compound and the reaction products formed by the chemical reaction of about 1 to about 5 parts of a nitro aromatic compound with about 0.3 to about 2 parts of an amino compound.

17. A lubricant assistant comprising a member of the group consisting of about 1 to about 5 parts of a nitro naphthalene in combination with about 0.3 to about 2 parts of an amine and reaction products thereof.

18. A lubricant assistant comprising a member ofthe group consisting of about 1 to about 5 parts of a nitro naphthalene in combination with about 0.3 to about 2 parts of an aromatic amine and reaction products thereof.

19. A lubricant assistant comprising a member of the group consisting of about 1 to about 5 parts of a nitro naphthalene in combination with about 0.3 to about 2 parts of a naphthylamine and reaction products thereof.

20. A lubricant assistant comprising a member of the group consistingof about 1 to about 5 parts of a-nitronaphthalene in 'combinationwith about 0.3 to about 2 parts of an-amine products thereof.

21. .A lubricant assistant comprising a member of the group consisting of about 1 to about 5 parts of a nitro naphthalene in combinationwith about 0.3 to'about 2 parts of alpha-naphthyh amine and reaction products thereof.

22. A lubricant assistant comprising a member of the group consisting of about 1 to about 5 parts of a-nitrcnaphthalene in combination with about 0.3 to about 2 parts of alpha-naphthylamine and reaction products thereof.

23. A lubricant assistant comprising about 1 to about 5 parts of a-nitronaphth-alene in combination with about 0.3 to about 2 parts of anthranilic acid.

24. A lubricant assistant comprising about 1 to about 5 parts of nitrobenzene in combination with about 0.3 to about 2 parts of dibutylamine.

25. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining there-between a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a-nitronaphthalene and about 0.3 to about 2 parts of anthranilic acid, and at and reaction the same time chemically acting upon such surfaces by means of said lubricant assistant.

26. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of nitrobenzene and about 0.3 to about 2 parts of dibutylamine, and at the same time chemically acting upon such surfaces by means of said lubricant assistant.

27. The method of retarding wearing and seizing of metallic bearing surfaces which comprises maintaining therebetween a film of a member of the group consisting of lubricating oils and greases containing at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a-nitronaphthalene and about 0.3 to about 2 parts of alpha-naphthylamine, and

at the same time chemically acting upon such surfaces by means of said lubricant assistant.

28. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a-nitronaphthalcne and about 0.3 to about 2 parts of anthranilic acid.

29. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of nitrobenzene and about 0.3

to about 2 parts of dibutylamine.

-30. Lubricating oils and greases having incorporated therein at least 0.1% of a lubricant assistant comprising the combination of about 1 to about 5 parts of a-nitronaphthalene and about 0.3 to about 2 parts of alpha-naphthylamine.

WILLIAM S. CALCOTT. ROBERT C. MCHARNESS. 

